UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Hints, Tips and Solutions (Do NOT post requests for help here)

Notices

Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

Reply
 
Thread Tools
Old 12th Mar 2020, 10:21 pm   #1
kevinaston1
Hexode
 
Join Date: Aug 2014
Location: Featherstone, West Yorkshire, UK.
Posts: 255
Default Cassette torque measurement.

From time to time, members need to measure this, but are unable to because of the silly prices charged for torque cassettes.

How about a gauge for under a fiver? Sounds good?

Torque on a cassette recorder is measured in g/cm. Since a cassette spool has about 1cm radius, measure the force applied to the rim of this and you have the measurement.

Scrap an old cassette and keep about 200mm of tape on each spool, at the end of the tape, tie a small loop.

Place the spool on the take up hub, tape on the left as the hub rotates clockwise. Hook a 0-100g spring pull gauge onto the loop and set the machine to play. Hold the pull gauge steady, and you have a measurement of the take up torque in grams per centimetre.

Measuring back tension is a little more difficult. Place the spool, on the supply hub with the tape on the right this time. Set the machine to play and SLOWLY (AND VERY STEADILY) pull on the spring gauge so it starts to unroll the tape. Not easy, but you should be able to make a reasonable measurement with care.

Individual spring pull gauges are available from Rapid Electronics, which is where I bought mine from, but there are many other suppliers. I bought a full set, since larger measurements are useful.


Finally, here is a story which will make you cry.

In the late 70’s, the company I worked for, distributed Audio Technica, who introduced a truly phenomenal mutitrack audio recorder called the RMX64; a six channel audio mixer with a 4 channel cassette recorder (standard and high speed).

I immediately placed a large order with AT Japan for a selection of spare parts so that I would be able to service any machine which came back. Along with the spare parts, they sent me a full set of standard and high speed test and alignment cassettes, in a mahogany case. I shudder to think what the value was, but it was probably around 1000 all those years ago.

At the end of 2012, I was made redundant by the company; to be replaced by two young panel/chassis swappers. A couple of years later, I spoke to the guy who was now in charge of the service department (no technical knowledge at all), to arrange to purchase some of my old test equipment and spare parts, one of which was said set of cassettes. He rang me back with a very good price on the test equipment and spare parts; none of which had been touched since I left.

What about the cassettes I asked? Sorry he said; we do not have those. I asked the lads in service what they were, neither of them knew what they were, and so I just threw them out.
Attached Files
File Type: pdf Cassette torque.pdf (13.8 KB, 90 views)
kevinaston1 is offline   Reply With Quote
Old 13th Mar 2020, 4:28 pm   #2
af024
Heptode
 
Join Date: Jan 2003
Location: Ashby-de-la-Zouch (it's not by the sea)
Posts: 829
Default Re: Cassette torque measurement.

A useful tip . Thank you for your posting. What a shame about the cassettes. Sadly this is more and more commonplace.

So what would be a 'typical' g/cm value (if there is such a thing as 'typical')?

Regards,

Andy
__________________
Now where on earth did I remove that from?
af024 is offline   Reply With Quote
Old 13th Mar 2020, 4:52 pm   #3
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 4,610
Default Re: Cassette torque measurement.

Great info, thanks!
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline   Reply With Quote
Old 13th Mar 2020, 7:56 pm   #4
kevinaston1
Hexode
 
Join Date: Aug 2014
Location: Featherstone, West Yorkshire, UK.
Posts: 255
Default Re: Cassette torque measurement.

Tape up torque varies from 25 to 50 g/cm; back tension from 2 to 12 g/cm. But it varies from model to model, it is normally given in the adjustments section of the service manual.
kevinaston1 is offline   Reply With Quote
Old 13th Mar 2020, 8:02 pm   #5
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,809
Default Re: Cassette torque measurement.

Quote:
Originally Posted by kevinaston1 View Post
What about the cassettes I asked? Sorry he said; we do not have those. I asked the lads in service what they were, neither of them knew what they were, and so I just threw them out.
Similar happened to me when we got chucked out of Philips. I had some good test gear stored away and around six months later went back to join in celebrations when an ex colleague was retiring. A spotty youth was 'in charge' of the lab and it soon became apparent that he knew nothing about testing or the equipment used. I enquired about the testgear and all that remained was a Marconi LCR bridge and an audio generator. I was able to obtain both for nothing (via another ex colleague) since they too were destined for the skip as he 'didn't know what they were'. What had been chucked? A combined wow and flutter and distortion meter, an RF spectrum analyser (newly purchased when digital broadcasting started in 1998), several RF signal generators and UHF modulators and a teletext generator....oh and around half a dozen of 'those voltage thingies' (his description of a multimeter)! They were electronic analogue types as well.
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is offline   Reply With Quote
Old 13th Mar 2020, 8:44 pm   #6
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: Cassette torque measurement.

Torque is measured in g,cm not g/cm. The SI unit is the N.m.
Eon tells me that a unit of electricity is measured in kW/hr. The SI measurement is 3.6MJ.
TrevorG3VLF is offline   Reply With Quote
Old 13th Mar 2020, 10:31 pm   #7
m0cemdave
Heptode
 
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 907
Default Re: Cassette torque measurement.

A company I used to do occasional work for had once owned a well-known recording studio, which had closed in the 1990's (along with all the others, in a minor example of a paradigm shift).

On the upper shelves in a corner of the workshop were boxes of spare parts. One day I had a look at what was there, and after recovering from my surprise, advised them not to throw any of it away as it was rather valuable and would fetch a substantial sum if auctioned (but if they did, please throw it in my direction...)

You can guess where this is going. Some months later, and in my absence, they had a clearout and skipped the lot.

Mechanical and electronic spares for Studers, Neves, SSL's, vintage condenser mic parts, a few KT66's...
m0cemdave is offline   Reply With Quote
Old 15th Mar 2020, 1:15 am   #8
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,100
Default Re: Cassette torque measurement.

Quote:
Originally Posted by TrevorG3VLF View Post
Torque is measured in g,cm not g/cm.
Isn't it more correct to say gf cm?
https://www.proaudio-revival.com/vhss-vhs.html
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 15th Mar 2020, 7:03 am   #9
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 3,872
Default Re: Cassette torque measurement.

Which reminds me of a little question I thought up years ago, and which none of the physics teachers at school could answer correctly :

Both torque and work have the same dimensions, a force times a distance. (In SI units, both are Nm (newton metres)). But while it is correct to use the joule as a unit of work, it is incorrect to use it as a unit of torque. What is the fundamental difference between the way torque and work are calculated?
TonyDuell is offline   Reply With Quote
Old 15th Mar 2020, 7:09 am   #10
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 3,872
Default Re: Cassette torque measurement.

Quote:
Originally Posted by rambo1152 View Post
Quote:
Originally Posted by TrevorG3VLF View Post
Torque is measured in g,cm not g/cm.
Isn't it more correct to say gf cm?
https://www.proaudio-revival.com/vhss-vhs.html
Yes. Strictly a gram is a unit of mass, not force (or weight).
TonyDuell is offline   Reply With Quote
Old 18th Mar 2020, 11:14 pm   #11
ben
Dekatron
 
ben's Avatar
 
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 5,941
Default Re: Cassette torque measurement.

Quote:
Originally Posted by m0cemdave View Post
You can guess where this is going. Some months later, and in my absence, they had a clearout and skipped the lot.

Mechanical and electronic spares for Studers, Neves, SSL's, vintage condenser mic parts, a few KT66's...
This is why, if in doubt it is probably best to just grab anything 'vulnerable' and then be prepared to return it later in the (seemingly very unlikely) event any questions are asked. It is better to say 'must have picked this up along with my stuff when clearing my desk' than regret its loss for a lifetime!
__________________
Regards,
Ben.
ben is offline   Reply With Quote
Old 29th Mar 2020, 5:26 am   #12
TIMTAPE
Octode
 
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,331
Default Re: Cassette torque measurement.

My first cassette torque gauge I made myself out of bits found at home. The spring came out of a Biro pen and the indicator pointer was from a paper clip.
This was for take up torque. I made another with a stronger spring (more up market Biro!) to test fast wind torques. The weakness of the simple design is that it stalls the spindle. You have to read it quickly before the End of Tape function shuts off the drive.

The other pictured is a professional Betamax torque gauge made I assume by Sony. It was sluggish when I first tested it a year or so ago so I dismantled it and found the oils in the mechanism had thickened, making the readings unreliable. A little cleaning and some light oil and it works well now.
Attached Thumbnails
Click image for larger version

Name:	Cassette torque gauge home made.jpg
Views:	61
Size:	53.6 KB
ID:	201741   Click image for larger version

Name:	Betamax cassette torque gauge.jpg
Views:	56
Size:	64.5 KB
ID:	201742  
TIMTAPE is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 3:38 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.